Dangers of lidocaine gel, other skin numbing agents: Is lidocaine really safe for mammograms?

by James Hubbard, M.D., M.P.H.

A while back, I blogged about a study that suggested over-the-counter lidocaine gel decreases the discomfort of a mammogram. (The gel numbs the skin after you rub it on.)

Recently, the FDA issued an alert reminding us that, although there were no serious side effects in the study, this same lidocaine gel and similar numbing agents can cause life-threatening side effects if you absorb too much through the skin.  Rarely, it has caused heart irregularities, seizures, breathing problems, coma and death.

A lot to risk for the minimal benefit found in the study, don’t you think?  In small amounts it appears to be safe, but the FDA recommends:

  • apply a thin layer and do not use over a large area of skin.
  • use the weakest strength available.
  • do not apply to irritated or broken skin.
  • do not wrap the skin after applying the gel.
  • do not apply heat after the application.

Not adhering to any of the above may increase your risk of the numbing agent absorbing into your bloodstream, which in turn increases risks of side effects.

It’s kind of a scare-of-the-day, but weighing risks to benefits, sounds to me like more than a dab won’t do.

In 2007 the FDA cited two instances of young women who were getting preparing for leg-hair laser removal by applying numbing cream and wrapping their legs.  Both died as a result of absorbing too much in the bloodstream.

The kind of medicines we’re talking about include lidocaine; tetracaine; benzocaine; and prilocaine cream, ointment or gel.

I use injectable lidocaine every day to numb the skin before repairing lacerations.  I think of it as pretty safe stuff as long as I don’t inject it directly into a blood vessel.  It makes you think.

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6 Responses to “Dangers of lidocaine gel, other skin numbing agents: Is lidocaine really safe for mammograms?”

  1. Judy Rodman Says:

    What a caring doctor you are… and always up on the latest news! This magazine continues in that tradition, always with the reader’s well-being in mind. Thank you!

    Judy Rodmans last blog post..Singing with others: A time to blend, a time to stand out

  2. James Hubbard, M.D., M.P.H. Says:

    What a nice compliment. Thanks.

  3. Dr. J Says:

    I’m familiar with a few cases of lidocaine being used to the point of toxicity! They involved high injectable dosage use, and usually in children, or outpatient plastic surgery. I would think this topical danger is a bit exaggerated. Not meaning to be unsympathetic, but if possible, I suggest not using anesthetic drugs unless absolutely necessary. I always thought the pain from mammograms was deeper than the surface, and due to compression of the breast.

    Dr. Js last blog post..Nibbles: More peanut products recalled, Japan says cloned meat OK, and how networks fuel inaugural coverage

  4. James Hubbard, M.D., M.P.H. Says:

    Yes Dr. J,
    The study using topical lidocaine before mammograms only helped a little with the discomfort.
    As far as the danger potential, there were the 2 deaths reported out of millions of uses. Still, death gets my attention and I won’t be slathering it on my scratched up legs and then wrapping with plastic:)
    I really never have found much practical use for the topical anyway.

    The most interesting point, to me, is a reminder to always look at the overall picture. One study shows a little benefit, another warns yeah but it has caused deaths if used improperly so don’t get carried away. It is about perspective.

  5. cathy Says:

    Love your thoughtful posts on new studies – especially when it conflicts with other studies. I’m wimpy, so I was going to go for the lidocaine before my first mammogram later in the year. Now, well, at least I’m informed.

    cathys last blog post..From Rice Krispies to crispy rice

  6. James Hubbard, M.D., M.P.H. Says:

    Thanks Cathy,
    See my previous post for a few safe tips than might ease your discomfort a bit.

    http://www.familydoctormag.com/blog/2008/07/lidocaine-gel-eases-discomfort-pain-from-mammograms/

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